Contact lenses have been used commercially to improve vision since the 1950s. The first contact lenses were made of hard materials. They were used by a patient during waking hours and removed for cleaning. Current developments in the field gave rise to soft contact lenses, which may be worn continuously, for several days or more without removal for cleaning. Although many patients favor these lenses due to their increased comfort, these lenses can cause some adverse reactions to the user. The extended use of the lenses can encourage the buildup of bacteria or other microbes, particularly, Pseudomonas aeruginosa, on the surfaces of soft contact lenses. The build-up of bacteria and other microbes can cause adverse side effects such as contact lens acute red eye and the like. Although the problem of bacteria and other microbes is most often associated with the extended use of soft contact lenses, the build-up of bacteria and other microbes occurs for users of hard contact lens wearers as well.
Others have taught that the addition of antibacterial agents such as metal salts to contact lenses can inhibit the growth of bacteria or other microbes. See, US 2004/0150788, which is hereby incorporated by reference in its entirety. In order produce manufacturing quantities of contact lenses containing antibacterial agents, processes to prepare these lenses must give consistent results. When some of the processes disclosed in US 2004-0150788 are used with different contact lens formulations, the contact lenses that are produced have variable amounts of antibacterial agents contained therein. Since the amount of antibacterial agent in every lens must be consistent from lot to lot, it is desirable to find process to prepare contact lenses containing antibacterial agents that produce a consistent product. This need is met by the following invention.